Flexible reflective insulating structures

ABSTRACT

A flexible reflective insulating structure includes a layer of flexible fiber-based material ( 10 ), and a flexible metallic layer ( 12 ) having a first surface of emissivity ( 14 ) less than 0.1. The metallic layer is attached to the layer of fiber-based material with its first surface facing towards the layer of fiber-based material. The fiber-based material is preferably attached to the metallic layer in a manner such that the emissivity of at least about 85% of the first surface, and preferably at least about 95%, and most preferably at least about 97%, is substantially unaffected.

FIELD AND BACKGROUND OF THE INVENTION

[0001] The present invention relates to reflective insulation and, inparticular, it concerns flexible reflective insulating structures forvarious uses.

[0002] Different types of insulation products reduce the heattransferred by conduction, convection and radiation to varying degrees.As a result, each provides different thermal performance andcorresponding “R” or “U” values (used to quantify heat transferproperties). The primary function of reflective insulation is to reduceradiant heat transfer across open spaces, which is a significantcontributor to heat gain in summer and heat loss in winter. The lowemittance metal foil (usually aluminum) surface of the product blocks upto 97% of the radiation and therefore a significant part of the heattransfer.

[0003] Aluminum foil is not, by itself, an effective thermal insulator.On the contrary, it is a metal with a relatively high thermalconductivity. When, on the other hand, a foiled surface is adjoined by a“still” airspace, a reflective space acts as an insulated barrier as itretards radiant heat (irrespective of heat flow direction) and thusreduces thermal transfer. In this context, it should be noted that theterm “reflective”, as used in reflective insulation, is in some ways amisnomer because the aluminum either works by reflecting heat(reflectance of 0.97) or by not radiating heat (emittance of 0.03).Whether stated as reflectivity or emittance, the performance (heattransfer) is the same.

[0004] The magnitude of that reduction of heat transfer is dependentupon maintaining the integrity of the airspace from a structuralstandpoint. The overall thermal efficiency of an airspace will vary withthe content of moisture (which increases the thermal conductivity ofair) and the presence of convective currents. The performance ofreflective surfaces in radiant barrier insulators is enhanced byproviding, maintaining and insuring an optimum adjoining airspace.

[0005] Currently available reflective insulating products havereflective surfaces on one or both outward-facing surfaces of a coremedium. Such products, however, suffer from numerous shortcomings.Specifically, such products are only effective when used in conjunctionwith a structure for ensuring an airspace adjacent to the reflectivesurfaces. This generally adds very significant labor costs toinstallation of the insulation. Furthermore, the properties of thereflective surfaces are extremely prone to degradation due to depositionof dust and dirt, and effects of corrosion on the surfaces. Thus, analuminum surface of initial emittance 0.03 may frequently be found toexhibit emittance values ten or more times greater due to accumulationof dirt. In moist or otherwise aggressive environments, the degradationmay be greatly accelerated by corrosion of the metal surfaces. In casesof applications in the building industry, such as within cavity walls,dust present during installation may reduce the effectiveness of theinsulation from the outset such that the theoretical values are neveractually obtained.

[0006] In an attempt to address these problems of degradation, U.S. Pat.No. 4,247,599 to Hopper proposes a layered structure which includes anintermediate metal layer is covered by a protective layer ofpolyethylene which is relatively transparent to infrared. The primarylow-emittance characteristic is provided by an exposed outer metal layerwhile the intermediate metal layer provides a “fail-safe feature” shouldthe exposed metal layer be completely degraded.

[0007] The solution proposed by Hopper offers very inferior results dueto the lack of an airspace adjacent to the intermediate metal layer.Thus, despite the relative transparency of the polyethylene, Hopperadmits that the metal-polyethylene combination exhibits an actualemittance value of 0.35, more than ten times greater than that ofaluminum exposed directly to an airspace.

[0008] An alternative approach to guarding the integrity of thereflective surfaces is to provide reflective surfaces facing inwardstowards airspaces defined by an internal structure. Examples of systemsof this type are described by U.S. Pat. No. 3,616,139 to Jones and U.S.Pat. No. 5,230,941 to Hollander et al. These patents disclose reflectiveinsulation panels made up of a honeycombed paper structure enclosed byinward facing foil reflective surfaces to form an insulative reflectivespace.

[0009] While the panels of Jones and Hollander et al. may provide highlyeffective insulation, their usefulness is limited by the rigid nature ofthe panels. Specifically, the panels are bulky and awkward to transport,and cannot be used at all in a wide range of applications for whichflexible insulating materials are required.

[0010] Finally, U.S. Pat. No. 5,549,956 to Handwerker discloses areduced thickness flexible insulating blanket for use in the curing ofconcrete. The blanket includes one or more heat reflective layer ofaluminum foil adjacent to an insulative layer of ¼ or ½ inch thicknessbubble-pack type material. The bubbles are disposed in spaced relationso as to define between them open air spaces adjacent to the foil.

[0011] The blanket of Handwerker also suffers from various shortcomings.Firstly, the contact surface of the insulative layer with the reflectivelayer is relatively high. Although not described in detail, it appearsfrom the illustrations that contact occurs over approximately 25% of thereflective surface, thereby greatly reducing the effectiveness of thereflective insulation. Additionally, the use of thin insulative layerscontaining open spaces with unrestricted air movement provides lowresistance to conductive and convective heat transfer through theblanket. Finally, any attempt to produce thicker, more effectiveinsulation by using multiple layers should reduce the flexibility of theblanket and lead to a bulky structure which would be costly andinconvenient to transport and handle.

[0012] There is therefore a need for flexible reflective insulatingstructures which would provide non-exposed reflective layers adjacent toan effective airspace which would also offer effective insulationagainst conductive and convective heat transport. It would also behighly advantageous to provide flexible reflective insulating structureswhich could be compactly stored and transported while being deployableto occupy an increased volume.

[0013] The common insulation fibers blankets, such as glass fiber ormineral wool, cause eye, skin and respiratory irritation. There arereports relating other serious health problems. The smoke of manypolymeric fibers produce high toxic materials. It would also highlyadvantageous to provide highly efficient insulating structure with nohealth side effects and less hazardous while burning.

SUMMARY OF THE INVENTION

[0014] The present invention provides flexible reflective insulatingstructures for use in buildings, tents and other applications.

[0015] According to the teachings of the present invention there isprovided, a flexible reflective insulating structure comprising: (a) alayer of substantially non-dust-generating, flexible fiber-basedmaterial; and (b)) a flexible metallic layer having a first surface ofemissivity less than 0.1, and preferably no more than 0.05, the metalliclayer being attached to the layer of fiber-based material with the firstsurface facing towards the layer of fiber-based material in a mannersuch that the emissivity of at least about 60% of the first surface, andpreferably at least about 95%, and most preferably at least about 97%,is substantially unaffected.

[0016] According to a further feature of the present invention, thelayer of fiber-based material is a non-woven material.

[0017] According to a further feature, of the present invention, thenon-woven material is configured to be compressible to a compressedstate for rolling to a rolled storage configuration and to recover whenunrolled to an uncompressed state, the non-woven material occupying avolume when in the uncompressed state which is at least about two timesa volume occupied by the non-woven material when in the compressedstate.

[0018] According to a further feature of the present invention, thenon-woven material has a bulk density of no more than about 1 kg/m², andpreferably within the range from about 0.4 to about 2 kg/m², per 10 cmthickness when in the uncompressed state.

[0019] According to a further feature of the present invention, thelayer of fiber-based material is formed primarily from polyester fibers.

[0020] According to a further feature of the present invention, thelayer of fiber-based material includes crimped fibers.

[0021] According to a further feature of the present invention, thelayer of fiber-based material includes low-melt fibers, having a meltingpoint surface significantly lower than the other fibers that form thefiber based body.

[0022] According to a further feature of the present invention, said lowmelt fibers are in a quantity within the range of about 15-40% by weightof the total fiber based body and preferably within the range of 20-30%by weight.

[0023] According to a further feature of the present invention, said lowmelt fibers, while being heated to the melting point, provide partialattachment between said fiber based body surface and the first surfaceof low emissivity of the flexible metallic layer.

[0024] According to a further feature of the present invention, thelayer of fiber-based material exhibits a reduced density of fibers in alayer adjacent to the metallic layer relative to an average density offibers in the fiber-based material.

[0025] According to a further feature of the present invention, thelayer of fiber-based material includes a first component of fibershaving a first diameter and a second component of fibers having a seconddiameter, the second diameter being at least twice the first diameter.

[0026] According to a further feature of the present invention, thelayer of fiber-based material is a woven material, the woven materialbeing processed to provide a plurality of raised fibers projectingoutwards from the woven material for supporting the metallic layer.

[0027] According to a further feature of the present invention, themetallic layer is a sheet of metal foil.

[0028] According to a further feature of the present invention, thesheet of metal foil has a second surface opposite to the first surface,the insulating structure further comprising a substrate layer attachedto the second surface.

[0029] According to a further feature of the present invention, thesubstrate layer is formed primarily from polymer material.

[0030] According to a further feature of the present invention, thepolymer material has a thickness of at least about 50 μm and contains atleast one additive chosen to enhance weatherproof properties of thepolymer material.

[0031] According to a further feature of the present invention, thepolymer material is selected to be a non-tearing material, the polymermaterial, the metallic layer and the fiber-based material being sewedtogether.

[0032] According to a further feature of the present invention, there isalso provided a sealant applied to the structure so as to seal regionswhich are sewed together.

[0033] According to a further feature of the present invention, thelayer of polymer material includes a plurality of reinforcing elements.

[0034] According to a further feature of the present invention, there isalso provided a second metallic layer associated with a rear surface ofthe substrate layer.

[0035] According to a further feature of the present invention, themetallic layer is implemented as a layer of metal deposited onto asurface of a flexible substrate layer.

[0036] There is also provided according to a further feature of thepresent invention, a tent comprising at least one wall formed from theinsulating structure of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

[0038]FIG. 1 is a schematic cross-sectional view through a basicone-sided embodiment of a flexible reflective insulating structure,constructed and operative according to the teachings of the presentinvention;

[0039]FIGS. 2A and 2B are schematic cross-sectional views showing theflexible reflective insulating structure of FIG. 1 in a compressedstorage state and an uncompressed state, respectively;

[0040]FIG. 3 is a schematic cross-sectional view through a double-sidedvariant of the embodiment of FIG. 1;

[0041]FIG. 4 is a schematic cross-sectional view through a furtherdouble-sided variant of the embodiment of FIG. 1 employing a polymerreinforcement layer;

[0042]FIG. 5 is a schematic cross-sectional view through anotherdouble-sided variant of the embodiment of FIG. 1 employing polymerreinforced reflective layers;

[0043]FIG. 6 is a schematic cross-sectional view showing animplementation of cavity wall insulation using a flexible reflectiveinsulating structure according to the present invention;

[0044]FIG. 7 is a schematic cross-sectional view showing animplementation of loft insulation using a flexible reflective insulatingstructure according to the present invention;

[0045]FIG. 8 is a schematic cross-sectional view through apolymer-reinforced embodiment of a flexible reflective insulatingstructure, constructed and operative according to the teachings of thepresent invention, including a woven fiber layer; and

[0046]FIG. 9 is a schematic cross-sectional view of an application ofthe present invention to a tent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] The present invention provides flexible reflective insulatingstructures for use in buildings, tents and other applications.

[0048] The principles and operation of flexible reflective insulatingstructures according to the present invention may be better understoodwith reference to the drawings and the accompanying description.

[0049] Referring now to the drawings, FIGS. 1-8 show variousimplementations and applications of flexible reflective insulatingstructures, constructed and operative according to the teachings of thepresent invention.

[0050] In general terms, each of the flexible reflective insulatingstructures of the present invention includes at least one layer 10 offlexible fiber-based material, and at least one flexible metallic layer12 having a first surface 14 of emissivity less than 0.1, and preferablyno more than about 0.05. Metallic layer 12 is attached to the layer 10of fiber-based material with first surface 14 facing towards layer 10.The fiber-based material of layer 10 is preferably attached to metalliclayer 12 in a manner such that the emissivity of at least about 85% offirst surface 14, and preferably at least about 95%, and most preferablyat least about 97%, is substantially unaffected.

[0051] It should be appreciated that the use of a flexible fiber-basedmaterial adjacent to the low emittance surface provides profoundadvantages over the aforementioned prior art. Firstly, the nature offiber-based materials lends itself to points or lines of contact withvery small total area, thereby facilitating attachment of the reflectivesurface with minimal interference with the low emittance properties ofthe surface. At the same time, the fiber-based material has been foundto behave almost exactly as an open airspace with respect to providing aradiant barrier with the reflective layer, while at the same timeproviding considerable resistance to air circulation so as to provideadditional effective conventional insulating properties againstconvective and conductive heat transfer. These and other advantages ofthe present invention will become clearer from the followingdescription.

[0052] With regard to the surprising observation that the fiber-basedmaterial behaves almost exactly as an open airspace in the radiantbarrier, without in any way limiting the scope of the present invention,it is believed that this observation has a sound basis in the theory ofreflective insulation. Specifically, it is known that the effectiveemittance E for a single reflective airspace bounded by two parallelsurfaces perpendicular to the direction of heat flow is given by:$E = ( {\frac{1}{ɛ_{1}} + \frac{1}{ɛ_{2}} - 1} )^{- 1}$

[0053] where ε₁ and ε₂ are the emittances of the of the respectivesurfaces. It follows that, if one of the surfaces has a low emittance(e.g. ε₁=0.039), even if the second surface approaches black-bodyemittance (e.g. ε₂=0.9), the overall emittance E of the system remainslow (E=0.039). Thus, so long as the contact area is kept to very lowlevels, the presence of fibers within the airspace opposite the lowemittance surface does not compromise the effectiveness of the radiantbarrier provided by the present invention.

[0054] Turning now to FIGS. 1, 2A and 2B, these show a first basicimplementation exemplifying the principles of the present inventionemploying a layer 10 of non-woven fiber-based material.

[0055] The use of non-woven material offers a number of particularadvantages. Most notably, the non-woven material is preferablyconfigured to be compressible to a compressed state as shown in FIG. 2A,typically for rolling into a rolled storage configuration, and torecover when unrolled to an uncompressed state as shown in FIG. 2B. Themaximum extent of volume recovery may take as much as a week to occur.The recovered uncompressed thickness T₂ is preferably greater than thecompressed thickness T₁ by at least a factor of 2, and in preferredcases, by a factor of at least about 5 up to as much as 8 times or more.Thus, a typical layer having a compressed rolled thickness of 2-4 mmmay, after volume recovery, provide a fiber-based layer of thickness10-30 mm. This provides profound cost savings during both storage andtransportation.

[0056] As mentioned earlier, it is a particular advantage of the use offiber-based materials that significant resistance is provided toconvective air currents. This effect is enhanced by the use ofrelatively small diameter fibers which offer larger flow damping. Smalldiameter fibers, on the other hand, have a reduced resiliency whichcould impede effective volume recovery. To address this problem, thefiber-based material preferably components of fibers with differentdiameters. Typically, a proportion of roughly 20% by weight ofrelatively large diameter fibers mixed with about 80% smaller diameterfibers has been found highly effective. The ratio of the diameters ofthe large diameter to small diameter fibers is at least 2:1 and usuallyconsiderably larger, depending upon the properties of the materialsused.

[0057] To avoid deposition of dust on surface 14, it is a particularlypreferred feature of the present invention that the fibers of layer 10are substantially non-dust-generating under normal conditions of use. Tothis end, the fibers used are preferably flexible fibers such that thematerial can be bent, folded, trampled over and otherwise maltreatedwithout breaking sufficient numbers of fibers to produce significantdust. For this reason, flexible fibers more commonly used in the textileindustry are generally preferred over the more brittle fibers often usedin the field of conventional insulation. Preferred examples include, butare not limited to, polyester fibers, textural polyamide fibers (nylon),and crimped acrylic fibers. In most preferred implementations, layer 10is formed primarily from polyester fibers, and most preferably, hollowpolyester fibers mixed with low melt polyester fibers.

[0058] In order to provide low contact surface area and an effectiveairspace for the reflective insulation, for most applications of thepresent invention, the fiber layer is preferably an “airy” structure ofdensity not exceeding about 4 kg/m² per 10 cm thickness (uncompressedstate). In preferred cases, low density non-woven materials of densityno more than about 0.4-2 kg/m² for 10 cm thickness are used.

[0059] Optionally, layer 10 may be processed so that a layer (preferably2-4 mm thick) adjacent to metallic layer 12 exhibits a reduced densityof fibers relative to the bulk of the fiber material. The properties ofthis surface layer are preferably equivalent to a density of 0-3-1.0kg/m² for 10 cm thickness. This may be achieved by known processes suchas by surface combing or by removal of a layer of the material from aninitially over-thick block. It should be noted, however, that theseadditional surface-thinning techniques are often unnecessary due to theinherently very low surface contact area of an airy fiber-based materialagainst an adjacent surface, as mentioned above.

[0060] In order to ensure the required bulk and structural integrity atsuch low densities, various precautions are preferably taken withrespect to the fiber formations within layer 10. Firstly, layer 10preferably includes crimped fibers, most preferably double crimped, suchthat the fibers are bent to exhibit non-coplanar portions. In thiscontext, the term “crimped” is used generically to refer to fibersprocessed by any process which results in frizzy fibers. This providesbetter mechanical support at relatively low fiber densities.Additionally, the production processes are preferably configured toproduce fibers with their primary extensional directions variedsufficiently to produce well-interconnected layers.

[0061] An exception to the general preference for low density is in thecase of thin fiber-based layers for use in tents and the like whererelatively high densities are preferred to provide sufficient structuralintegrity. Specifically, such structures typically use high densitylayers of 2-5 mm non-woven or woven material with relatively lowcompressibility.

[0062] Turning now to metallic layer 12, this may most simply beimplemented as a sheet of metal foil. Alternatively, in implementationsin which a substrate is provided adjacent to the metallic layer (seeFIGS. 4 and 5 below), layer 12 may be formed by vapor deposition on asurface of the substrate. Most commonly, aluminum is used, althoughother low-emittance metals not very rapidly corroded could besubstituted therefor. Examples include, but are not limited to, brass,copper, gold, silver, platinum. The low-emittance surface is preferablypolished, and most preferably highly polished. Optionally, the metalfoil sheet may be treated to also provide low emittance characteristicson its outward-facing surface. However, it should be noted that theprimary operative reflective (low emittance) surface according to thepresent invention remains the inward-facing surface 14 which isprotected from the problems of deterioration described above.

[0063] Attachment of metallic layer 12 to fiber-based layer 10 ispreferably achieved by use of adhesive by one of a number of techniques.According to a first preferred technique, the adhesive is applied to thefiber-based material by a zero-loaded roller in spaced relation to layer10 so as to come in contact exclusively with fibers projecting outwardsfrom the layer sufficiently to contact metallic layer 12. The metalliclayer is then brought into contact with the adhesive-coated fibers. Theadhesive used is preferably low-viscosity so as to avoid forming largedroplets which could spread on contact with the metallic layer.Alternatively, the metallic layer is than brought into contact with lowmelt fibers while being heated to their melting point and slightlypressed to avoid forming of large droplets which could spread on themetallic layer spoiling its low emissivity.

[0064] Alternative attachment techniques employ forming a pattern ofadhesive across a small surface area of either the fiber layer or themetallic layer before bringing the two layers together. A suitablepattern is typically a rectangular, hexagonal or other grid of smalldots corresponding to a total area of less than 40%, and preferably lessthan 5%, or even less than 3%, of the total surface area.

[0065] Suitable adhesives include, but are not limited to, various hotglues air-drying glues and heat-activated adhesives.

[0066] A further alternative attachment technique is the use ofminimal-pressure localized welding of fibers of said fiber-basedmaterial such that they contact less than about 15%, and preferably lessthan 5%, or even 3%, of first surface 14.

[0067] Turning now to various additional implementations of the presentinvention, it is a preferred feature of most preferred implementationsthat layer 10 is enclosed on two opposite faces. This serves to enhancethe convective insulating properties of the structure as well as forminga substantially closed unit to prevent penetration of dirt and dustthrough to the low emittance surfaces. For further enhanced sealing, thestructure may optionally be enclosed along its side edges, either duringproduction or during installation, by a thin layer of plastic or thelike.

[0068] In addition to blocking dust and air flow, where the seal isprovided by an additional metallic layer, the structure provides adouble radiant barrier function, greatly enhancing the insulatingproperties. An example of such a structure is shown in FIG. 3, eachinterface being fully equivalent to that described with reference toFIG. 1.

[0069]FIG. 4 illustrates a further variation in which the insulatingstructure further includes a substrate layer 16 attached to the outersurface of metallic layer 12. In this case, as mentioned earlier,metallic layer may be either a foil layer bonded to the substrate layeror a coating deposited thereon. Depending upon the intended application,substrate layer 16 may be chosen to provide the desired degree ofmechanical strength, wear resistance, weatherproofing or other physicaland mechanical properties. Examples of suitable substrate layersinclude, but are not limited to, textiles, paper and various polymersincluding polyethylene, PVC, nylon and polyesters. For certainapplications, the use of textile substrates and other non-tearingpolymer substrates offer particular advantages since they make itpossible to sew the structure. In such cases, sewing may become theprimary mode of interconnection of the various layers of the structure.To ensure that the locations of the threads do not compromise theinsulative properties, a sealant is preferably applied to the regionssewed. Additionally, or alternatively, thread may be used which swellson exposure to moisture so as to seal the apertures formed by serving.For all-weather applications such as for all-purpose tents, a mostpreferred option is plasticized PVC with additives for LW and weatheringresistance.

[0070] By way of example, with brief reference to FIG. 9, there is showna tent formed with at least one wall implemented as an insulatingstructure according to the present invention. In this context, the word“tent” is used to refer generically to any structure formed primarily bya flexible material which is sup ported by a support structure or whichis air-supported. The polymer material for such applications preferablyhas a thickness of at least about 50 μm, and preferably at least about500 μm, and contains at least one additive chosen to enhanceweatherproof properties of the material.

[0071] For increased structural strength, polymer implementations ofsubstrate layer 16 may include a plurality of reinforcing elements 18.The reinforcing elements are chosen to provide improved tensilestrength. Examples of suitable reinforcing elements include, but are notlimited to, elongated fibrous materials, woven and non-woven cloths.

[0072] Turning now to FIG. 5, this shows a further variant in which asecond metallic layer 20 is either attached to, or vapor deposited onto,a rear surface of substrate layer 16. This forms a reinforced sandwichstructure with emittance properties equivalent to a sheet of foil withtwo low-emittance surfaces Although, as mentioned earlier, the principalreflective barriers of the present invention are provided by surfacesfacing towards fiber-based layer 10, the outward facing surfaces oflayers 20 may in many cases be deployed to provide a further enhancementto the reflective insulation properties.

[0073]FIGS. 6 and 7 illustrate certain applications of the presentinvention. FIG. 6 illustrates a cavity wall 22 within which theinsulating structure of FIG. 3 or 5 has been fitted. Preferably, thestructure is mounted via a number of spacer elements 24 with a small gapfrom the internal wall surface. The resulting airspace provides anadditional barrier to conductive heat flow and, in the case of thestructure of FIG. 5, provides an additional radiant barrier. On theother side, a larger gap may be required, such as to accommodateelectric cables 26 or the like. However, it should be appreciated thatthe present invention may readily be configured to fill virtually anythickness of cavity to whatever degree desired, either by use of asingle thick fiber-based layer 10, or by repeating part or all of thelayer structure.

[0074]FIG. 7 shows an application of the present invention to loftinsulation applied over a concrete or plaster ceiling 28. Here, thereflective insulation structure is shown implemented as a multi-layerstructure with two layers 10 of fiber-based material each lopped by ametallic layer 12. At least the intermediate metallic layer 12 ispreferably implemented as the sandwich structure described withreference to FIG. 5 above, thereby providing an additional upward-facingradiant barrier. Optionally, an additional polymer layer 30 may bedeployed below the lower fiber-based layer 10 to seal the bottom of theinsulating structure.

[0075] It should be noted in the context of this and otherimplementations of the invention that there is considerable flexibilityas to the form in which the structures are supplied and transportedprior to deployment. Thus, in the case of FIG. 7, the structure may besupplied is a reflective sheet (or “sandwich”) with a fiber-based layerattached to opposite surfaces. The uppermost metallic layer may then beattached during installation. Alternatively, the upper layers may besupplied as a unit similar to that described with reference to FIG. 5which is either attached to, or simply positioned overlying, aseparately deployed fiber-based layer 10. In a further alternative, thestructure could be formed by combining the structures described withreference to FIGS. 1 (the lower portion of FIG. 7) and 3 (the upperportion).

[0076] Turning finally to FIG. 8, it should be noted that the presentinvention may also be implemented using a layer of woven fiber-basedmaterial 32. Typically, woven materials of thickness up to about 2.5 mmare believed to be economically viable for such applications. Thematerial may optionally be reinforced by use of a polymer backing 36 orthe like.

[0077] In many cases, a sufficient proportion of fibers projectirregularly from the main body of the woven material to allowlow-contact-area attachment of the metallic layer without furtherpreparation. In other cases, however, it is preferable to process thematerial, typically by the process known a “raising”, to provide aplurality of raised fibers 34 projecting outwards from the wovenmaterial for supporting metallic layer 12.

[0078] Although typically less compressible than the non-wovenimplementations of the present invention, raised fibers 34 generallyprovide a significant degree of resilient compressibility such thatthickness reductions of about a factor of 2 may be achieved.

[0079] It will be appreciated that the above descriptions are intendedonly to serve as examples, and that many other embodiments are possiblewithin the spirit and the scope of the present invention.

What is claimed is:
 1. A flexible reflective insulating structurecomprising: (i) a layer of substantially non-dust-generating, flexiblefiber-based material; and (ii) a flexible metallic layer having a firstsurface of emissivity less than 0.1, said metallic layer being attachedto said layer of fiber-based material with said first surface facingtowards said layer of fiber-based material in a manner such that saidemissivity of at least about 85% of said first surface is substantiallyunaffected.
 2. The insulating structure of claim 1, wherein said firstsurface-has an emissivity of no more than 0.05.
 3. The insulatingstructure of claim 1, wherein said metallic layer is attached to saidlayer of fiber-based material by adhesive, said adhesive being presenton less than about 15% of said first surface.
 4. The insulatingstructure of claim 1, wherein said metallic layer is attached to saidlayer of fiber-based material by minimal-pressure localized welding offibers of said fiber-based material such that they contact less thanabout 15% of said first surface.
 5. The insulating structure of claim 1,wherein said metallic layer is attached to said layer of fiber-basedmaterial in a manner such that said emissivity of at least about 95% ofsaid first surface is substantially unaffected.
 6. The insulatingstructure of claim 1, wherein said metallic layer is attached to saidlayer of fiber-based material in a manner such that said emissivity ofat least about 97% of said first surface is substantially unaffected. 7.The insulating structure of claim 1, wherein said layer of fiber-basedmaterial is a non-woven material.
 8. The insulating structure of claim7, wherein said non-woven material is configured to be compressible to acompressed state for rolling to a rolled storage configuration and torecover when unrolled to an uncompressed state, said non-woven materialoccupying a volume when in said uncompressed state which is at leastabout two times a volume occupied by said non-woven material when insaid compressed state.
 9. The insulating structure of claim 8, whereinsaid non-woven material has a bulk density of no more than about 4 kg/m²per 10 cm thickness when in said uncompressed state.
 10. The insulatingstructure of claim 8, wherein said non-woven material has a bulk densitywithin the range from about 0.9 to about 2 kg/m² per 10 cm thicknesswhen in said uncompressed state.
 11. The insulating structure of claim1, wherein said layer of fiber-based material is formed primarily frompolyester fibers.
 12. The insulating structure of claim 1, wherein saidlayer of fiber-based material includes crimped fibers.
 13. Theinsulating structure of claim 1, wherein said layer of fiber-basedmaterial exhibits a reduced density of fibers in a layer adjacent tosaid metallic layer relative to an average density of fibers in saidfiber-based material.
 14. The insulating structure of claim 1, whereinsaid layer of fiber-based material includes a first component of fibershaving a first diameter and a second component of fibers having a seconddiameter, said second diameter being at least twice said first diameter.15. The insulating structure of claim 1, wherein said layer offiber-based material is a woven material, said woven material beingprocessed to provide a plurality of raised fibers projecting outwardsfrom said woven material for supporting said metallic layer.
 16. Theinsulating structure of claim 1, wherein said metallic layer is a sheetof metal foil.
 17. The insulating structure of claim 16, wherein saidsheet of metal foil has a second surface opposite to said first surface,the insulating structure further comprising a substrate layer attachedto said second surface.
 18. The insulating structure of claim 17,wherein said substrate layer is formed primarily from polymer material.19. The insulating stricture of claim 18, herein said polymer materialhas a thickness of at least about 50 μm and contains at least oneadditive chosen to enhance weatherproof properties of said polymermaterial.
 20. The insulating structure of claim 18, wherein said polymermaterial is selected to be a non-tearing material, said polymermaterial, said metallic layer and said fiber-based material being sewedtogether.
 21. The insulating structure of claim 20, further comprising asealant applied to said structure so as to seal regions which are sewedtogether.
 22. The insulating structure of claim 18, wherein said layerof polymer material includes a plurality of reinforcing elements. 23.The insulating structure of claim 17, further comprising a secondmetallic layer associated with a rear surface of said substrate layer.24. The insulating structure of claim 1, wherein said metallic layer isimplemented as a layer of metal deposited onto a surface of a flexiblesubstrate layer.
 25. The insulating structure of claim 24, wherein saidsubstrate layer is formed primarily from polymer material.
 26. Theinsulating structure of claim 25, further comprising a second metalliclayer associated with a rear surface of said layer of polymer material.27. A tent comprising it least one wall formed from the insulatingstructure of claim 1.